A known opening-closing device is used as an opening-closing device for a backdoor (as a tailgate) of a vehicle as described in Japanese Patent Laid-Open Publication No. 2003-41853. With the known opening-closing device, the backdoor is opened both electrically and manually. The known opening-closing device described in Japanese Patent Laid-Open Publication No. 2003-41853 includes an electromagnetic clutch. When the backdoor is electrically operated to open and close, the electromagnetic clutch is energized for transmitting a rotational force of an actuator including an electric motor and a deceleration mechanism to an opening-closing mechanism connected to the backdoor. In the meantime, with the known opening-closing device, when the backdoor is manually operated to open and close, the transmission of the rotational force is cut by disengaging a transmitting member included in the electromagnetic clutch and a transmitted member from each other so that the backdoor is opened and closed without being affected by the resistance generated by the transmission of the reverse rotational force from the opening-closing mechanism side for rotating the actuator in reverse. For example, the known opening-closing device described in Japanese Patent Laid-Open Publication No. 2003-41853 includes a spring affecting the transmitted member to be disengaged from the transmitting member.
With the foregoing known construction, the transmitted member has to be attracted to the transmitting member with the strong force against the biasing force of the spring so that the rotational force is transmitted by the electromagnetic clutch when transmitting the rotational force of the actuator to the opening-closing mechanism. Thus, the known construction increases the size of the electromagnetic clutch. In the meantime, because the spring is configured to transmit the rotational force and to disengage the transmitted member from the transmitting member, the construction of the spring assumes complicated, which increases the manufacturing cost.
A need thus exists for an opening-closing device which includes an electromagnetic clutch with small and simple construction.